This invention relates to a method for the reproduceable formation of material layers by vapor deposition, sputtering, chemical deposition, etc. In particular, the formation of semiconductor layers through diffusion or ion implantation with at least one parameter of the material layer being measured during the formation of the layer and used as a measuring signal in a digital evaluation circuit for on-line control of the layer formation process is disclosed.
Electrical, i.e. time or frequency-dependent measuring methods where a defined change in one value in the electrical system being studied (for example, current) is measured, and the measurement of this value, including evaluation of the measuring signal (for example, voltage) as a function of time or frequency, are used in the study of complex reactions and conducting processes in electrochemistry (Techniques of Electrochemistry, E. Yeager, A. J. Salking, Wiley-Interscience, N.Y. 1972).
Furthermore, when used with solid-state cells, these methods can separate the electrode reactions from the conduction processes in the interior of the solid-state material (M. Meyer et al., Solid State Ionics 9, 10 (1983), pages 689 to 694).
Electrical conduction in solid-state material is determined by intrinsic properties such as current flow through the material areas, the degree of doping in the material, and the temperature of the materials and extrinsic properties such as the structure (texture), morphology, and production conditions of the particular material.
In the field of thin-film technology, slight deviations in the processing conditions used in a particular production method will produce thin layers with significant structure and morphology changes, which cause large property changes in the conductivity, capacitance, inductivity, adhesion capability, hardness, density, and resistance to wear and tear, to oxidation and to corrosion.
EP A2 00 33 507 shows the use of direct current measurements for determining the layer thickness and/or the structure changes of the electrically conducting layers formed during on-line-type production methods. For determining the temperature a resistance thermometer is used. This method is suitable only for conductivity determination of electrical conductors due to the use of direct current.